1. Field
Embodiments of the present disclosure generally relate to methods for treating hydrocarbons. More particularly, embodiments of the present disclosure relate to methods for deasphalting hydrocarbons.
2. Description of the Related Art
The supply of light, sweet, crude oil is diminishing, requiring refineries to process heavier crude feed stocks such as those produced in Western Canada, Venezuela, Russia and the United States. While varying widely in composition, these heavy crude hydrocarbons generally have similar characteristics: API gravity of less than 25; high metal content, especially nickel and vanadium; high sulfur, nitrogen and oxygen content; and high levels of Conradson Carbon Residue (“CCR”). The heavy crude oils can also have high acid content measured as Total Acid Number (TAN). Since these heavy crude hydrocarbons generally do not flow at ambient conditions, treatment at the point of extraction is often necessary prior to introducing the heavy crude hydrocarbons to the transportation network, i.e. pipelines
Solvent deasphalting has been used to remove high viscosity asphaltenic compounds from heavy crude hydrocarbons, providing a low viscosity deasphalted oil suitable for transportation. Additionally, the deasphalted oil has a reduced concentration of the metals content and CCR levels as compared to the heavy crude hydrocarbons. The asphaltenic compounds contain the majority of the metals, CCR, sulfur containing compounds, nitrogen containing compounds, and the like. A disadvantage of solvent deasphalting, however, is that the light hydrocarbons in the heavy crude hydrocarbon can degrade the efficiency of the solvent used in the deasphalting process. To prevent this degradation, the heavy crude hydrocarbons are typical pretreated to separate and remove the light hydrocarbons prior to solvent deasphalting. Typical pretreatment processes include atmospheric distillation and vacuum distillation.
However, the installation of one or more pretreatment processes in addition to one or more solvent deasphalting processes, at the point of extraction can have multiple drawbacks. Such drawbacks include: increasing the overall footprint of the solvent deasphalting process to include one or more upstream treatment processes: increasing quantity and complexity of equipment required to pretreat the heavy crude; increasing initial capital cost; increasing ongoing operating costs; and reducing overall reliability of the solvent deasphalting process due to the increase in mechanical components.
There is a need, therefore, for an improved, more economical, and/or more efficient process for pretreating a heavy crude hydrocarbon prior to solvent deasphalting.